Java applets are limited for security reasons: they can't access special hardware on the computer of the visitor (hey, do they have this hardware, anyway?) except if you sign your applet.
General advices: go to Java preferences, enable the Java console to see the error messages that can be thrown at you. And when you update the jar, don't forget to clear the Java cache, in the same dialog.

PS.: and that's an Integration and Hardware topic, not a Processing Implementation one, unless you mean using another language like JavaScript.